A significant trend throughout integrated circuit (IC) development is the downsizing of IC components. As the size reduces, the performance requirements become more stringent. Also, as devices continue to shrink in size, the channel region continues to shrink as well. For metal-oxide-semiconductor field effect transistors (MOSFETs), increased performance requirements have generally been met by aggressively scaling the length of the channel region. However, such a short channel length faces high electric field and manufacturing limits.
With regard to the scaling of integrated circuits, the current performance of devices is highly relative to the total resistances of such devices. The device drive currents are inversely proportional to the total resistance. The total resistance includes a channel resistance RCH and an external resistance REXT. In 45 nm technology and below, the external resistance REXT dominates performance of the device drive currents. In addition, it is found that contact resistance holds a majority of the external resistance REXT. However, high contact resistance causes the device drive currents to reduce. In order to obtain higher drive currents, a new structure with a low contact resistance and its manufacturing method are required.